internal_link: Parse "/is/starred" internal links.

Signed-off-by: Zixuan James Li <zixuan@zulip.com>

Author: PIG208

lib/model/internal_link.dart

@@ -199,10 +199,11 @@ Narrow? _interpretNarrowSegments(List<String> segments, PerAccountStore store) {
     switch (isElementOperands.single) {
       case IsOperand.mentioned:
         return const MentionsNarrow();
+      case IsOperand.starred:
+        return const StarredMessagesNarrow();
       case IsOperand.dm:
       case IsOperand.private:
       case IsOperand.alerted:
-      case IsOperand.starred:
       case IsOperand.followed:
       case IsOperand.resolved:
       case IsOperand.unread:

test/model/internal_link_test.dart

@@ -242,10 +242,11 @@ void main() {
         switch (operand) {
           case IsOperand.mentioned:
             testCases = sharedCases(const MentionsNarrow());
+          case IsOperand.starred:
+            testCases = sharedCases(const StarredMessagesNarrow());
           case IsOperand.dm:
           case IsOperand.private:
           case IsOperand.alerted:
-          case IsOperand.starred:
           case IsOperand.followed:
           case IsOperand.resolved:
           case IsOperand.unread: